Abstract[14C]‐Labelled methazole was incubated in six soils at 25°C and with soil moisture at field capacity. Under these conditions, methazole was unstable, the concentration declined following first‐order kinetics with half‐life values in the soils ranging from 2.3 to 5.0 days. The main degradation product was 1‐(3,4‐dichlorophenyl)‐3‐methylurea (DCPMU) which was more stable than the parent compound. After about 160 days, DCPMU accounted for 30 to 45% of the initial methazole concentration. Degradation of methazole and DCPMU was affected by soil temperature and moisture content. With methazole, half‐lives in one soil at field capacity moisture content and temperatures of 25, 15 and 5°C were 3.5, 8.7 and 31.1 days respectively. The half‐life at 25°C was increased to 5.0 days at 50% of field capacity and 9.6 days at 25% of field capacity. A proportion of the initial radioactivity added to the soil could not be extracted and this proportion increased with time. After 160 days this unextractable radioactivity accounted for up to 70% of the amount applied.